Building permits are required for all structures with the exception of a structure that is less than 200 square feet with no electrical, plumbing or mechanical.
R1-6 is a single-family residence district that aims to create stable, functional neighborhoods. In this zoning type, accessory structures can be as close as 3 feet to rear and side property lines and can have a maximum height of 15 feet.
If your structure is less than 120 square feet, you will not require a building permit. Please refer to section 706 of the Zoning Ordinance for full text on accessory structures.
In most residentially, zoning districts, accessory structures can be located in the rear of your property, can be as close as 3 feet to the rear and side property lines, with a maximum height of 15 feet. The building must be 6 feet away from other structures.
Any shed or structure that is greater than 200 square feet requires a building permit. If a storage shed is equal to or under 200 square feet, no permit is required.
The quick and simple answer is: you usually don't need a permit if the shed is 120 square feet or less. In California, most jurisdictions have adopted the 120 square foot rule. If your shed area is larger than 120 square feet, it needs a building permit. If it's less than that, it doesn't.